For decades the fundamental basis for assessing auditory perception has been assumed to be short time Fourier transformation. This has been the case because the construction of the cochlea point in that direction. This assumption has however caused several unexplainable phenomena. Among them it has never been revealed how the human hearing perceives vowels, and how it in general perceives sound “pictures”.
The ear originally evolved as a warning system that should warn against enemies that try sneaking toward you, and it is typical sound from breaking twigs that gives you such a warning. Such a sound is a pulse and it might have a very short duration, which is not suitable for analysis by Fourier transformation because the information contained by the pulse will be averaged through the analysis. Also the frequency spectrum of a signal has the weakness that outstanding frequencies in the spectrum might come from different sources without the possibility to tell. This is a big problem by analysing vowels in speech recognition, where background noise might be interpreted as false formants.
Fourier transformation is a mathematical tool that eliminates the time dimension and is therefore by nature not suitable for pulse analysis. Because pulses are very important, the dynamic behaviour of the signal is very important, and the method for analysis must be based on tools that reflect the physical behaviour of the cochlea. The invention provides a time and frequency analysis that simulates the behaviour of human ear.
The method of the invention is developed for speech analysis, but the method is suited for other purposes as well. Thus, the results of the method of the invention may be used for identification of sound or vibration or speech or quality measurement of products where sound or vibration reveals the quality of the products. The method of the present invention may also be used in connection with speech recognition or speech coding and decoding in narrowband telecommunication. In its broadest aspect the result of the invention may be used for identification or representing features, which a human or animal ear can perceive, but it is not restricted thereto.
Oscillation analysis is a general analysis that also may be used outside the frequency range that can be perceived by a human or animal ear such as high frequency telecommunication.